MOSCOW, July 20 (RIA Novosti) - Ukraine's Anti-Monopoly Committee (AMKU) announced Tuesday that it has no evidence to prove that growth in gas prices has been caused by a collusion between Russian oil companies operating in Ukraine, the Gazeta daily reported.

TNK-BP Ukraina, LITASCO-Ukraina, LUKOIL-Ukraina, LiNOS (the Lisichansk oil refinery) and LUKOIL-Odessa Oil Refinery were under the AMKU's review.

The case against the oil companies was opened in April on the instructions of Prime Minister Yulia Tymoshenko, who blamed them for the sharp rise in fuel prices during spring fieldwork when prices shot up by 10% to 15%. Tymoshenko said Russian companies were trying to discredit the new Ukrainian administration.

The Economics Ministry set a ceiling on retail fuel prices and AMKU pledged to prove the existence of a collusion between the companies to jointly raise the prices. Other forces were also drawn into the campaign. Alexei Ivchenko, head of state-owned Naftogaz Ukrainy, said it was necessary to reprivatize the country's biggest oil refinery in Lisichansk, owned by TNK-BP.

The attack on the oil firms triggered a fuel crisis. President Viktor Yushchenko intervened, abolishing the state regulation of prices and in effect blamed Tymoshenko for the crisis.

This left AMKU to either incriminate the companies and fuel a fresh scandal, or vindicate them entirely and embarrass Tymoshenko.

Anti-Monopoly Committee head Alexei Kostusev tried to please both sides. He promised Tuesday to support Tymoshenko's efforts "aimed at bringing order to the country's oil products market."

In mid-July, the seasonal growth of fuel consumption began in Ukraine, to peak during autumn fieldwork. As early as July, oil prices may rise by 10% and diesel could go up by 15%.